Consolidated Statements of Cash Flows (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009
Cash flows from operating activities:
Net income	$ 555	$ 566	$ 550
Adjustments to reconcile net income to net cash flows from operating activities:
Depreciation and amortization	611	561	549
Deferred income taxes and amortization of investment tax credits	374	710	645
Changes in regulatory assets and liabilities	(23)	4	5
Other, net	(25)	(58)	(32)
Changes in other operating assets and liabilities:
Accounts receivable and other assets	(42)	(14)	(5)
Derivative collateral, net	4	(102)	57
Inventories	(59)	(26)	(39)
Income taxes receivable, net	275	(96)	(206)
Accounts payable and other liabilities	(34)	(135)	(24)
Net cash flows from operating activities	1,636	1,410	1,500
Cash flows from investing activities:
Capital expenditures	(1,506)	(1,607)	(2,328)
Purchases of available-for-sale securities	0	0	(21)
Proceeds from sales of available-for-sale securities	0	0	36
Other, net	(23)	(6)	5
Net cash flows from investing activities	(1,529)	(1,613)	(2,308)
Cash flows from financing activities:
Net proceeds from (repayments of) short-term debt	652	36	(85)
Proceeds from long-term debt	399	0	992
Proceeds from equity contributions	0	100	125
Repayments and redemptions of long-term debt and capital lease obligations	(588)	(16)	(144)
Preferred stock dividends	(2)	(2)	(2)
Common stock dividends	(550)	0	0
Other, net	(2)	(1)	(20)
Net cash flows from financing activities	(91)	117	866
Net change in cash and cash equivalents	16	(86)	58
Cash and cash equivalents at beginning of period	31	117	59
Cash and cash equivalents at end of period	$ 47	$ 31	$ 117